Method and means for controlling high-frequency oscillators



Feb. 25, 1947. N. H. YOUNG, JR

METHOD AND MEANS FOR CONTROLLING HIGH FREQUENCY OSCILLATORS Filed Oct. 6, 1942 CONTROLL/I'BLE PULSE GENEfifl TOR INVENTOR. NORM/FIN H. YOU/V6, JR.

Patented Feb. 25, 1947 "METHOD AND MEANS FOR CONTROLLING HIGH-FREQUENCY OSCILLATORS Norman H. Young, Jr., Jackson Heights, N. Y.,

assignor to Federal Telephone and Radio Corporation, a corporation of Delaware ApplicationOctober 6, 1942, Serial No. 460,944

6 Claims. (Cl. 250-36) the times of starting and stopping of a high frequency vacuum tube oscillator in accordance with the width of a controllable selected pulse or series of pulses.

A still further object of this invention is to provide a method and means for controlling the period of operation of a high frequency vacuum tube oscillator in accordance with the width of a selected applied pulse.

A more specific objectof this invention is to control the period of operation of a high frequency vacuum tube oscillator by varying its-grid bias in accordance with the width of a predetermined selected pulse,

Generally speaking, the invention is directed to the control of the period of operation of a high frequency vacuum tube oscillator by differentiating a pulse into positive and negative pulses of sufficient value to control the blocking and unblocking of the oscillator in accordance with the width of the pulse.

Other objects and advantages of the present invention will appear to those skilled in this art from the following description of a preferred embodiment of the invention, illustrated in the accompanying drawings, wherein:

Fig. 1 is a circuit diagram of the Vacuum tube oscillator control circuit in accordance with the present invention;

Fig. 2 shows a series of curves illustrating the operation of various elements of the circuit illustrated in Fig. 1; and

Fig. 3 shows a series of curves illustrating the operation of the same elements as the'curves in Fig. 2, but under slightly different predetermined conditions. v r

In accordance with the present invention the period of operation of a vacuum tubeoscillator may be controlled by means of a pulse generator 8, the width of the generated pulses and their frequency being controllable in a manner well known to the art. The'generated pulses are preferably amplified as by triode it having the usual cathode l2, grid is, and anode It, the amplified pulses being then passed through the pritube oscillator.

made by way of example to Fig. 2 showing at (a) mary winding of a suitable high frequency transformer IS. The plate supply for the tube lfl may be derived from a suitable high voltage source indicated at 2!) which may be by-passed by a condenser 22.

The secondary of the transformer i8 is connected to the high frequency oscillator to be 'controlled, illustrated by way of example as a suitable push-pull radio frequency oscillator. While the invention is applicable to any high frequency vacuum tube oscillator, for the purposes of illustrating the principles of the present invention, the latter has been shown as including a tank coil E l, the mid-point of which is connected to the secondary of the transformer la, the other end of which is connected to the grid bias supply for the oscillator which, in turn, may be bypassed by a suitable condenser 25. The'end terminals of the tank coil 24 are connected by leads 26' and 28 to the grids of the push-pull tubes 3%! and 32. A condenser 35 is connected in shunt with the tank coil 2t. Cathodes lit and 4B of the tubes 3i) and 32 are connected together and.

grounded, while anodes 34 and 1-38 are connected I to opposite ends of another tank coil 42 shuntedby a suitable condenser Ma The mid-point of. the tank coil 42 may be connected to a high voltage plate supply source 46.

The operation of the aforedescribed circuit depends upon the action of the transformer l8 to differentiate the pulses derived from the ampli fier Ill. The action of such a suitably designed transformer to properly differentiate pulses is, however, known to the art. If, for example, a positive pulse of predetermined width. is applied to the primary winding of the transformer IS, the pulse will be differentiated into a short posi tive pulse produced by the steep leading edge of the applied pulse and, ashort negative pulse resulting from the steep trailing edge of the applied pulse. The positive and negative pulses so produced will appear at the terminals of the secondary winding and will be spaced apart as de termined by the width of the applied pulse.

The differentiating effect made possible by the use of a transformer it, is applied in a manner now to be described to the control of the vacuum In this connection, reference is generated pulses 5d, which may be two of a series of similar pulses initiated at times t1 and #1. Through the action of the differentiating transformer the leading edge of the pulse 54 will produce a positive pulse it of short duration, whilejthe trailing edge of the pulse 54"wil1 pro 3 duce a negative pulse 72 of short duration at a time is after the time of the initiation of the pulses t1. The period t1t2 between the positive and negative pulses it and 12 is equal to the width, in time, of the pulse 56. This will be true for all pulses'fi i at later times such as t'1t' 2. In the preferred form of the invention illustrated, the high frequency oscillator is provided with such a grid bias that it is normally non-conductive. If, for example, axis 48 in Fig. 2(b) repre-- sents the amount of negative bias normally ap-.- plied to the oscillator tubes relatively to a threshold voltage represented by the line 5! sufiicient to start and sustain radio frequency oscillations, it will be clear that when the positive pulse 18 produced by the leading edge of the pulse 54 is of suficient amplitude to bring the applied grid voltage above the threshold 56, the oscillator will immediately be placed in operation. Such operation will continue until the negative bias is sufiiciently great to block the oscillations during any part of the oscillating period, and in Fig. 2(b) this negative value is represented by the line 52. Accordingly, when the trailing edge of the pulse 54 produces the negative pulse '52 of sufiicient amplitude to bring the applied voltage'upon the grid of the oscillator tubes below the value represented by the line 2, the operation of the oscil-i later will cease. Fig. 2(0) illustrates the modulated envelope 63 produced by the control action of the pulses l8 and 12.

A study of the above-described sequence of operations will immediately show that the period of operation of the oscillator is predetermined and controlled by the width of the pulse 4 as well, of course, as by the frequency of such pulses. Accordingly, by varying the width of the controlling pulse the period of operation of the oscillator may likewise be altered. This is shown by way of example in Fig. 3 in which the generated. pulse 62 is wider than the pulse 54. As a result the differentiated positive and negative pulses H, 73 will be spaced further apart in timeand the resultant operation of the oscillator as represented by the envelope 88 Will extend over greater periods t1ts, t'1t'3.

It has now been clearly shown that by means of the present invention the period of operation of a high frequency oscillator can be positively selectively controlled by varying the width of a generated pulse. The time between oscillating, periods willbe controlled by the frequency of, the applied pulse, This operation may, of course, be reversed if, instead of generating positive pulses in the example given, the pulses applied to the differentiating circuit are negative pulses. In such a case, as will at once be apparent to thoseskilled in this art, the application of first a negative pulse and then a positive pulse to the oscillator will control the period during which such oscillator is not operating. In such event the actionwill be exactly the reverse of that described in the example given, in that the period between pulses will determine the period of operation of the oscillator, while the width of the pulse will determine the period during which the oscillator is blocked.

Various other changes may be made in this in- I vention, all coming within the scope of the basic principles thereof. In addition to the modified example just given, it will also be obvious to those skilled in this art that the operation of the oscilj 4 circuit itself are of relatively little importance and it makes no difference whether the oscillator is of the push-pull type, as illustrated, or utilizes only a single tube.

While I have described above the principles of my invention in connection with certain specific examples, it is to be clearly understood that this description is made only by way of example and not as limitation on the scope of my invention, as set forth in the objects of my invention and the accompanying claims.'

I claim:

1. The method of controlling a high frequency oscillator of the type which is inoperative in the absence of initial energization but which when once energized will continue to oscillate without further energization, which includes the steps of generating a pulse of a predetermined selected width, producing positive and negative pulses of predetermined amplitude, each corresponding in time to an edge of said generated pulse, and controlling the starting and stopping of said oscillator in accordance with said positive and negative pulses, whereby the width of the generated pulse determines the period of operation of said oscillator.

2. In combination, a, highfrequency oscillator including a vacuum tube, means for normally biasing said tube to such a value as to render the oscillator normally inoperative but insufficient to prevent operation of the oscillator when the tube is once energized, means for generating a pulse of a predetermined selected width, means for producing pulses of opposite value corresponding in time to the leading and trailing'edges of said generated pulse, said pulses having sufiicient amplitude to control the operation of said tube, and means for applying said pulses to said tube for blocking or unblocking'the same, whereby the period of blocking and unblocking of the tube is controlled by. the selected width of the pulse.

3. In combination, a high frequency oscillator including a vacuum tube, means for normally biasing the grid of said tube below cut-off to such a value as to render the oscillator normally inoperative but insufiicient to prevent operation of the oscillator when once energized, means for generating a pulse of a predetermined selected width, means for producing pulses of opposite value respectively corresponding in time to the leading and trailing edges of said generated pulse, the positive pulse having such a value as to negative the bias on said tube and render the same conducting and the negative pulse having such a value as to block the tube, and means for applying said positive and negative pulses to the grid of said tube.

4. The method of controlling a high frequency oscillator of the type including an electron discharge device biased to such a value as to render the oscillator inoperative until said device is energized but insufficient to prevent operation of the oscillator when said device is once energized,

which includes the steps of generating a pulseof predetermined width, producing positive and negative pulses respectively corresponding to the leading and trailing edges of the first pulse, and applying said positive and negative pulses to said biased electron discharge device, the positive pulses being of such value as to render the device conductive and the negative pulses being of such value as to block the operation of said device, whereby the period of operation of said oscillator is controlled by the width of the generated pulse.

5. In combination, a high frequency oscillator,

5 including a vacuum tube, means for normally biasing the grid of said tube below cut-off to such a value as to render the said oscillator normally inoperative but insufficient to prevent operation of the oscillator when once energized, means for generating a pulse of predetermined width, means for producing a positive pulse corresponding in time to the leading edge of the generated pulse and a negative pulse corresponding in time to the trailing edge of the generated pulse, said positive pulse having such a value as to negative the bias of said tube and render the same conducting, and said negative pulse having such a value as to block said tube, and means for applying said positive and negative pulses to the grid of said tube.

6. The method of controlling a high frequency oscillator of the type including an electron discharge device whose control element is biased to such a value as to render the oscillator inoperative until said device is energized but insufiicient to prevent operation of the oscillator when said 6, device is once energized, which includes the steps of generating a pulse of predetermined width, producing positive and negativelpulses respectively corresponding to the leading and trailing edges of the first pulse, and applying said positive and negative pulses to the control element of said electron discharge device, the positive pulses being of such value as to render the device conductive and the negative pulses being of such value as to block the operation of said device, whereby the period of operation of said oscillator is controlled by the width of the generated pulse.

NORMAN H. YOUNG, JR.

REFERENCES CITED UNITED STATES PATENTS Name Date Kotowski et al Nov. 28, 1939 Number 

